We propose an approach to studies of cell survival, mutagenesis, DNA replication, repair replication, and the assessment of DNA damage in mammalian cells as they relate to the cell cycle. Our objective is to compare these parameters and develop appropriate hypotheses concerning the relationships between the cell cycle and cellular responses to radiation and chemicals. Specifically, we will compare the survival and mutagenic responses as a function of the cell cycle phase in response to UVL, UVL-like chemicals, X-rays, and X-ray-like chemicals; determine the cell cycle dependence of radiation and chemical DNA-damage recognized by damage specific enzymes; and investigate ultraviolet light-irradiated G1-phase cells for UVL-specific DNA synthesis that may be involved in the bypass of DNA damage and to compare the UVL-specific synthesis with that induced by selected chemicals.